1. Field of the Invention
The present invention relates to a process for the production of reinforced rubber articles. More particularly, the present invention relates to a process for the production of reinforced rubber articles formed from polyester, more preferably polyethylene terephthalate, yarn embedded into a rubber stock, wherein the yarn is coated with an aqueous emulsion which contains an epoxy silane, and wherein silica particles are included in the rubber stock. The present invention also relates to reinforced rubber articles produced in accordance with the process. The preferred reinforced rubber articles are pneumatic passenger tires which have excellent adhesion of tire cord to rubber.
2. Description of the Prior Art
Polyester tire cord requires the application of an adhesive layer to obtain bonding to the rubber. Two types of adhesive systems, a single dip and a double dip adhesive system, have been developed to meet this need.
In the double dip system, polyester cords are treated with a first dip which is a dispersion of a phenol-blocked methylene bis-phenylene diisocyanate, an epoxy resin, wetting agents and water. The treated cord is cured, then treated with a second dip of resorcinolformaldehyde-latex and cured again.
In the single dip system, an adhesive is incorporated in either a spin finish or an overfinish for application to the polyester yarn. The polyester yarn is plied and/or twisted into cords which are treated with a resorcinolformaldehyde-latex dip and cured. The need for the blocked diisocyanate dip in cord processing is eliminated by this system. Low carboxyl polyester yarn treated with this system has very good ammonolytic and hydrolytic stability, but has poor adhesion to rubber when made into tire cord. Further, while regular carboxyl polyester yarn shows acceptable adhesion to rubber under normal curing temperatures, a reduction of the curing temperatures has been found to adversely affect adhesion to rubber.
The present invention significantly improves yarn to rubber adhesion of polyester tire cords treated with the single dip system for (a) low carboxyl polyester yarn wherein normal dip curing temperatures are utilized, and (b) regular carboxyl polyester yarn wherein reduced dip curing temperatures are utilized.
The closest prior art is believed to be U.S. Pat. No. 3,672,977 to Dardoufas, 3,730,892 to Marshall et al., 3,778,406 to Klotzer et al. and British Patent Specification 1,230,982 to Jervis et al.